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Synovial Fluid
Published in Verna Wright, Eric L. Radin, Mechanics of Human Joints, 2020
Pierre Geborek, Frank A. Wollheim
It is not clear how die intraarticular structures remain intact and still are able to glide against one another underthese large decreases in pressure. Levick suggested a “pillar” model in the joint cavity due to the irregularities of synovium thickness. The thicker parts of synovium serve as pillars when meeting the opposite surface in the joint cavity, permitting synovial fluid to move freely in the arches between them (41). In the synovium the situation may be similar to that in cartilage. In the cartilage, large amounts of fixed negative charges of the proteoglycans repel one another, thereby preventing the collapse of cartilage upon joint load. In the synovium interstitium, negatively charged fixed glucosaminoglycans may function as pillars, preventing synovium collapse (see also Fig. 1). In the SF, global domains of hyaluronan probably separate the intraarticular surfaces even when pressure decreases (Fig. 2).
Positional information in the extracellular matrix
Published in David M. Gardiner, Regenerative Engineering and Developmental Biology, 2017
Anne Q. Phan, Md. Ferdous Anower-E-Khuda
Proteoglycans are composed of a core protein, with one or more GAG chains covalently attached. The GAG side chains are unbranched, long polysaccharides decorated with sulfate residues at different positions and are hence often referred to as sulfated GAGs. The GAGs are highly negatively charged repeating disaccharide units composed of N-acetylated hexosamine and D-/L-hexuronic acid. The GAG chain length and degree of sulfation of PGs are extremely heterogeneous and play critical roles in cellular signaling mechanisms. To date, six types of GAGs have been described: heparin (Hep), heparan sulfate (HS), chondroitin sulfate (CS), dermatan sulfate (DS), keratan sulfate (KS), and hyaluronan (HA). Based on the localization of PGs, four major classes have been identified: intracellular, cell surface, pericellular, and extracellular PGs.
Nonlinear Mechanics of Soft Biological Materials
Published in Heather N. Hayenga, Helim Aranda-Espinoza, Biomaterial Mechanics, 2017
The mechanical behavior of soft tissues is endowed by the cellular interactions with fibrous protein networks and an amorphous gel-like ground substance consisting of water, glycoproteins, glycosaminoglycans, and proteoglycans. Glycosaminoglycans such as hyaluronan, chondroitin sulfate, dermatan sulfate, and heparin sulfate, to name a few, are hydrophilic, unbranched polysaccharides. Mechanically, they serve as lubricants and shock absorbers in tissues while occupying a large volume per mass. Proteoglycans such as decorin, versican, syndecan, and aggrecan, to name a few, are glycosaminoglycans covalently attached to a protein core. Glycosaminoglycans and proteoglycans, through their affinity for water, contribute to a high resistance to compressing loading and add to the viscous behavior of soft tissues. Fibronectin and laminin are glycoproteins of the ECM that play a role in cell–cell and cell–substrate adhesion and have specific binding sites for other ECM components. Cells connect to ligands of the ECM through adhesion complexes that include transmembrane receptor proteins such as integrins (Griendling et al., 2011). Integrins link the intracellular stress fibers to the ECM enabling the transduction of extracellular signals into the cell. The acute mechanical influence of integrins and their ligands is most obvious in activated muscle cells that can shift the stress–strain curve.
Glucosamine modulates membrane and cellular ionic homeostasis: studies on accelerated senescent and naturally aged rats
Published in Egyptian Journal of Basic and Applied Sciences, 2022
Komal Saraswat, Raushan Kumar, Syed Ibrahim Rizvi
Glucosamine (GlcN), 2-amino-2-deoxy-D-glucose, is a naturally occurring amino sugar found in the human body. It is an important component of glycoproteins, proteoglycans, and glycosaminoglycans, which is a major component of joint cartilage [10]. GlcN has a potent background as a glycolytic inhibitor [11,12]. Its entry into cells is stimulated by insulin and involves the glucose-transporter system [13]. GlcN in its phosphorylated form (GlcN-6-phosphate), acts as an inhibitor of hexokinase, the first enzyme of glycolysis. Researchers have introduced a novel biological and pharmacological application of GlcN as a caloric restriction mimetic (CRM) [14]. Recently, we have reported that GlcN supplementation results in an improvement in aging biomarkers in erythrocytes and plasma by inducing a transient mitohormetic increase in ROS [15].
Study on the poroelastic behaviors of the defected articular cartilage
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
Yuqin Sun, Ningning Wang, Jianhao Yu, Yang Yan, Hao Dong, Xiaogang Wu, Meizhen Zhang, Yanqin Wang, Pengcui Li, Xiaochun Wei, Weiyi Chen
As the sole cellular component in cartilage tissue, the main responsibility of chondrocytes is to maintain the stability of the extracellular matrix (Benders et al. 2013). However, this stability is destroyed when the cartilage is defective, and chondrocytes needs to remodel it to find a new balance (Peng et al. 2021). A significant reduction in the synthesis of proteoglycans was observed in human osteoarthritis samples, which resulted in changes of the permeability and elastic modulus of the cartilage matrix. In turn, changes of the structure and composition of the extracellular matrix affect the fluid flow inside the tissue, which causes the chondrocytes to behave abnormally. It has been found that during the development of osteoarthritis, the elastic modulus of the extracellular matrix decreases (Armstrong and Mow 1982; Kiviranta et al. 2008) and the permeability increases (Nieminen et al. 2004; Knecht et al. 2006). Thus, different elastic modulus E (0.4, 0.5, 0.6, and 0.69 MPa) and permeability k (3 × 10−18m2, 4 × 10−18m2, 5 × 10−18m2, 6 × 10−18m2) were simulated. The average values of p and v around the defect under different parameters are shown in Figures 16 and 17. On the whole, the p and v show the opposite trend, that is, when the p increases, the v decreases instead. The softening of the solid matrix and the increase in permeability both lead to a decrease in p and an increase in v.
Development of biomimetic electrospun polymeric biomaterials for bone tissue engineering. A review
Published in Journal of Biomaterials Science, Polymer Edition, 2019
Sugandha Chahal, Anuj Kumar, Fathima Shahitha Jahir Hussian
Bone is a composite material which consists of both fluid and solid phases. Bone is hard because the organic extracellular collagenous matrix is impregnated with inorganic minerals of calcium phosphate, principally hydroxyapatite Ca10(PO4)6(OH)2. Calcium and phosphate account for roughly 65 to 70% of the bone's dry weight. The bone mineral has Ca/P ratio of 1.67, but it can vary from 1.37 to 1.87 due to the presence of additional minerals ions (refer to Table 1). Collagen fibers account approximately 25 to 30% of the bone matrix. Bone is mostly composed of type-I collagen and a very small percentage of type-IV. The type-I collagen molecules form the collagen fibrils and these collagen fibrils together form the tropocollagen in a parallel array [41]. Surrounding the mineralized collagen fibers is a ground substance consisting of protein polysaccharides, or glycosaminoglycans (GAGs), primarily in the form of complex macromolecules called proteoglycans. The GAGs assist to cement the various layers of mineralized collagen fibers together. The organic part of bone is responsible for its flexibility, while the inorganic material gives elasticity to bone [48,52,54].